Motor drives are power conversion systems used to provide power to a driven electric motor by converting received input power. The motor load, in turn, may be used in a variety of different applications. In submersible well pumps, a driven pump motor is used to drive a screw or centrifugal type pump, typically to extract fluid from a well. In normal operation, the pump motor turns in a forward direction to pump the fluid upward within the well tube. If the associated motor drive loses power, however, the pump motor will stop rotating, and previously pumped fluid will start draining back down into the well, causing the rotor of the pump motor to spin in the reverse direction. If the motor is constructed with permanent magnets, the reverse rotation of the pump motor creates a back EMF which may lead to significant voltage that can damage the motor and/or degrade components in the motor drive, including a DC bus capacitor at the input of the drive inverter. Screw type pumps in particular can accelerate in the reverse direction to a point where the back EMF creates a significant voltage that is greater than the nominal voltage of the motor. Moreover, reverse rotation of the pump motor allows fluid to drain back down into the well, whereby the pumping work that was done prior to power loss must be redone later when power is restored. A similar situation occurs in motor driven cranes, in which the load on a crane motor may tend to reverse the motor rotation during power loss events. Accordingly, a need remains for techniques and apparatus to protect motor drives and driven motors from damage due to excess back EMF, and to prevent the motor from reaching high reverse speeds for power loss situations.